Taiwan Patent Publication No. TWI508903, TWI508899 are previous creations of the applicant. Both the two patents disclose a cap and a container. The cap is composed of a cap body and a retaining member. The retaining member is assembled to the cap body to form a sealing space for filling an additive. By rotating the cap body, the additive can be released from an exposed opening of the retaining member so that the additive can be mixed with the liquid in the container.
The rotation of the cap body is to unscrew the cap body, and then the retaining member is moved upward along with the cap body to expose the opening of the retaining member. After the additive is released from the cap body, the container is shaken to mix the additive with the liquid in the container. For drinking, the cap body is unscrewed to disengage from the cap body. During the process, it is necessary to take many actions for mixing the additive with the liquid of the container. In addition, the additive may drip from the cap body when the cap is removed from the container.